Thermal stability of spin-valves incorporating amorphous CoNbZr under and capping layers

We introduce amorphous CoNbZr-based spin-valves (SVs) where CoNbZr substituted Ta layers that have been traditionally used for under and capping layers. The purpose of this study was to investigate thermal stability of the new structure at elevated temperatures. A comparison was also made with a similarly structured Ta-based SV. Magnetoresistance (MR) ratio and exchange bias field (H _ex) of CoNbZr-based SV increased up to about 50% (from 4.5% to 6.8%) and 52% (from 294 Oe to 448 Oe), respectively, after annealing at 300°C for 240 min. The root-mean-square (rms) surface roughness values for CoNbZr and Ta single layers were 0.07 nm and 0.43 nm, respectively, indicating that an amorphous CoNbZr offers much smoother surface than the Ta layer. Because CoNbZr-based SVs possess fine and dense microstructures, they were able to resist interdiffusion at elevated temperature, resulting in an improvement in thermal stability. In addition, Mn diffusion into the pinned CoFe layer might be reduced probably due to the fact that CoNbZr capping layer provided almost equal chemical potential for Mn diffusion into the pinned CoFe layer.